1. Field of the Invention
The present invention relates to the field of reducing nitrogen oxide emission from internal combustion engines and turbines, and more particularly to a novel means of adding hydrogen prepared by means of a novel burner from a portion or part of the main engine fuel whether it be gaseous or liquid.
2. Brief Description of the Prior Art
It is well known that nitrogen oxides (NO.sub.x) form at the high temperatures normally associated with combustion processes and that operating an engine at lean conditions with excess air lowers temperature and, therefore, decreases NO.sub.x. However, decades of engine and turbine studies have shown that lean combustion limits for all fuels are above those where NO.sub.x emissions are below specified goals. Natural gas and gasoline are examples where lean combustion has been pushed to its limit and where it has been found that hydrogen addition increases this limit to where NO.sub.x output is acceptably low. However, means to obtain hydrogen for this purpose are beset with problems.
Problems and difficulties have been encountered when the supply of hydrogen is provided by materials carried in a separate tank which can be extremely heavy and requires pressurization. As examples, methanol, hydrogen or ammonium nitrate can produce hydrogen when added to an engine combustor.
However, these add to the fuel and so reduce the volumetric storage capacity which lowers overall performance, and results in complications through use of secondary materials. Hydrogen stored in the pressurized container which holds methane (Hythane) can also be used, but this causes about 75 percent reduced engine range for each percent hydrogen used because of its very low energy content on a volumetric basis, and also requires special means to enable safe storage of hydrogen.
A more favorable method to obtain hydrogen is by properly treating a portion of the main engine fuel itself. This does not require storing and using a new expendable and can be accomplished with little or no loss of fuel energy. Hydrogen may be produced from fuels by high-temperature decomposition, such as those listed in Greiner, U.S. Pat. No. 4,350,133. The actual patent discloses a fuel burner and decomposer combination on which hot gases produced from the burner heat a secondary flow of fuel within a heat exchanger to temperatures where it decomposes to form hydrogen. It is intended for use with methanol as fuel, which can uniquely decompose without formation of solid carbon "soot" which can harm the engine process. The burner of the aforementioned patent cannot efficiently combust when fuel rich, where otherwise hydrogen is produced. Hydrogen can also be produced by reacting the fuel with water to produce hydrogen through a "reforming", process. Such a process, however, requires involved catalytic means to bring about the water-fuel reaction, a heat input for its endothermic reaction, stored water or means to obtain it from the engine exhaust, etc. In addition, it often is difficult to obtain rapid and accurate flow response Because of such factors, the reformer process does not lend itself to an engine process.
The fuel may also be reacted with a deficiency of air to produce hydrogen. Doing, so, however, is challenging because the excess fuel is not highly reactive and therefore difficult to involve in the reaction. For this reason, such previous processes relied on on catalysts and complex hardware, which tended to make the process virtually unusable. Thus, Houssman, et al, U.S. Pat. No. 4,033,133 teaches the use of special high temperature catalyst coupled with intensive preheat of the reactants to combust fuel with air to produce hydrogen. Such catalytic devices, by their nature, are complex, difficult to control, and require undesirably long start-up times. Thus, they do not lend themselves to an engine process.
Therefore, a long-standing need has existed to provide a novel apparatus and means for accomplishing a technology breakthrough for a simple means of producing hydrogen from fuel in a simple burner without the catalyst or special pressurized hydrogen or related storage means normally considered.